'\" et
.TH SIGSUSPEND "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
sigsuspend
\(em wait for a signal
.SH SYNOPSIS
.LP
.nf
#include <signal.h>
.P
int sigsuspend(const sigset_t *\fIsigmask\fP);
.fi
.SH DESCRIPTION
The
\fIsigsuspend\fR()
function shall replace the current signal mask of the calling thread
with the set of signals pointed to by
.IR sigmask
and then suspend the thread until delivery of a signal whose action is
either to execute a signal-catching function or to terminate the
process. This shall not cause any other signals that may have been
pending on the process to become pending on the thread.
.P
If the action is to terminate the process then
\fIsigsuspend\fR()
shall never return. If the action is to execute a signal-catching
function, then
\fIsigsuspend\fR()
shall return after the signal-catching function returns, with the
signal mask restored to the set that existed prior to the
\fIsigsuspend\fR()
call.
.P
It is not possible to block signals that cannot be ignored. This is
enforced by the system without causing an error to be indicated.
.SH "RETURN VALUE"
Since
\fIsigsuspend\fR()
suspends thread execution indefinitely, there is no successful
completion return value. If a return occurs, \-1 shall be returned and
.IR errno
set to indicate the error.
.SH ERRORS
The
\fIsigsuspend\fR()
function shall fail if:
.TP
.BR EINTR
A signal is caught by the calling process and control is returned from
the signal-catching function.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
Normally, at the beginning of a critical code section, a specified set
of signals is blocked using the
\fIsigprocmask\fR()
function. When the thread has completed the critical section and
needs to wait for the previously blocked signal(s), it pauses by
calling
\fIsigsuspend\fR()
with the mask that was returned by the
\fIsigprocmask\fR()
call.
.SH RATIONALE
Code which wants to avoid the ambiguity of the signal mask for thread
cancellation handlers can install an additional cancellation handler
which resets the signal mask to the expected value.
.sp
.RS 4
.nf

void cleanup(void *arg)
{
    sigset_t *ss = (sigset_t *) arg;
    pthread_sigmask(SIG_SETMASK, ss, NULL);
}
.P
int call_sigsuspend(const sigset_t *mask)
{
    sigset_t oldmask;
    int result;
    pthread_sigmask(SIG_SETMASK, NULL, &oldmask);
    pthread_cleanup_push(cleanup, &oldmask);
    result = sigsuspend(sigmask);
    pthread_cleanup_pop(0);
    return result;
}
.fi
.P
.RE
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "Section 2.4" ", " "Signal Concepts",
.IR "\fIpause\fR\^(\|)",
.IR "\fIsigaction\fR\^(\|)",
.IR "\fIsigaddset\fR\^(\|)",
.IR "\fIsigdelset\fR\^(\|)",
.IR "\fIsigemptyset\fR\^(\|)",
.IR "\fIsigfillset\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<signal.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
